The invention relates to a method of catching a broken printed web which is gripped downstream from a printing unit and more particularly downstream from the last printing unit of a web feed rotary printing press between a driven roll and at least one rotor which is able to be pivoted against the roll in response to the signal of a switch sensing breaking of the web. Furthermore as seen from another aspect, the invention relates to an apparatus comprising a gripper device arranged following a printing unit and more particularly following the last printing unit of a web feed rotary printing press so that one side of the gripper device comprises a roll driven by a drive device and the other side comprises a rotor which is mounted on a carrier arranged to be moved by an engagement device into engagement with the roll in response to a switch sensing breaking of the web.
German patent publication 3,822,496 refers to a device of this type, in the case of which the roll is driven at the same speed as the printing press. If the web is not wound onto the roll, something that occurs when the web is not printed or is only printed to a slight extent, it is impossible with this known device to draw the web taut with the catching device after the web has necessarily already become loose after breakage, at the time it is caught. Therefore there is the danger of the web flying wildly around and/or of the web running up into contact with an adjacent cylinder of the printing mechanism which may lead to a wrap-around. If in fact the web wraps onto the roll of the web catching device, and this is to be expected in the case of a heavily printed web, the resulting increase in the effective diameter of the roll will mean that the surface speed is greater than the speed at which the web is able to be supplied so that it will break off again, even though the web is loose after the first break. The tension force acting on the web is however not limited and there is the danger of breakage and a second wrap-around. The arrangement described in the German patent publication 3,822,496 is therefore not sufficiently reliable.
German patent 3,215,473 relates to a device of the type described in the case of which the roll is to be driven at the same speed as the web or slightly faster. The drive device associated with the roll is however inherently rigid so that during the time in which the arrangement is slowed down to a halt there is the same ratio between the speeds of the web and the roll. In this respect as well there is therefore the danger that the web will be drawn excessively tight and accordingly be broken off again if the printing press is not braked sufficiently promptly.